Replicon typing of plasmids in Escherichia coli producing extended-spectrum beta-lactamases.
OBJECTIVE
Escherichia coli producing CTX-M-15 and CTX-M-14 extended-spectrum beta-lactamases (ESBLs) are spreading worldwide. The aim of this work was to investigate the replicons involved in the emergence and spread of ESBLs in relation to ESBL type.


METHODS
A collection of 125 TEM, SHV and CTX-M ESBL-producing E. coli strains was analysed. The replicons carrying the ESBLs and the total plasmid content of the strains have been characterized by PCR replicon typing in relation to the type of ESBL. The ESBL replicons were then compared with the replicon content of E. coli strains carrying TEM-1 or inhibitor-resistant TEM (IRT) beta-lactamases.


RESULTS
IncF plasmids were the most frequently carried replicons in our collection, but none carried TEM ESBL. Of TEM ESBLs, 67% were carried on IncA/C replicons except for TEM-52 genes, which were carried preferentially on IncI1 replicons. Although CTX-M enzymes can be carried by various replicons, the great majority of genes encoding CTX-M-14 and CTX-M-15 ESBLs were carried by IncF replicons, as were TEM-1 and IRT beta-lactamases.


CONCLUSIONS
Resistance genes borne by the narrow host-range IncF replicon spread readily as this replicon is well adapted to E. coli. This is observed for blaTEM-1 and blaCTX-M-15 and, to a lesser extent, for blaCTX-M-14. Transposition immunity seems to play an important role in the diffusion process.
Marcadé
Geraldine
G
Université Pierre et Marie Curie-Paris-6, Faculté de Médecine, Site Saint-Antoine, Laboratoire de Bactériologie, EA 2392 Paris, France.
Deschamps
Catherine
C
Boyd
Anders
A
Gautier
Valérie
V
Picard
Bertrand
B
Branger
Catherine
C
Denamur
Erick
E
Arlet
Guillaume
G
D004251:DNA Transposable Elements; D004269:DNA, Bacterial / Q000235:genetics*; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics*; D006801:Humans; D010957:Plasmids / Q000145:classification*; D016133:Polymerase Chain Reaction / Q000379:methods; D012093:Replicon; D001618:beta-Lactamases / Q000096:biosynthesis / Q000235:genetics*
D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D001618:beta-Lactamases